New FIP Treatment

 

Frankie, enjoying our front porch in better days

Molnupiravir Shows Promise in Treating FIP Cats

Feline Infectious Peritonitis -- more commonly known as FIP. It's the diagnosis no cat parent ever wants to receive. Caused by a relatively benign feline coronavirus as ubiquitous as the common cold in humans, in some cats it morphs into a three-stage spiral toward death -- like syphilis in humans. It most commonly claims cats under two years old, but can also affect older cats in rare cases. 

FIP can manifest in several ways: 

• effusive - the "wet" form that produces three stages: upper respiratory, gastrointestinal, and the chest or abdominal cavity filling with fluid
• non-effusive - the "dry" form that causes granuloma-type tumors on the major organs
• neurological - a dry form of the disease, made worse due to the blood-brain barrier being ineffective at preventing the virus from infiltrating the cerebrospinal fluid, forming lesions in the central nervous system (CNS, brain and spine)
• ocular - another dry form of FIP causing eye lesions that are often the first noticeable symptom, due to the virus infecting the aqueous humor of the eyes; may also be accompanied by brain lesions

My FIP Experience

Our own beloved Frankie, pictured above, was several years old when he started showing symptoms of what appeared to be an upper respiratory infection that wouldn't go away. Several months later, he developed what our vet diagnosed as pancreatitis, and we had to put him on a special diet for it. Less than a year after that, I looked down at him from above and he looked like a cartoon bodybuilder: slim in the hips but HUGE in the chest area. He was also short of breath and panting for air. I rushed him to the emergency vet, where they drained a lot of fluid from his chest that they said was "teeming with bacteria." He was in the hospital for a week, but died there on a Sunday morning. 

In just under two years after the first stage, Frankie was gone. But that was in 2009, before there was any hope of a different outcome. We could only guess based on his symptoms that FIP was what claimed him, since there was not even an accurate test for FIP then; most kittens are exposed to the coronavirus when very young and have no lasting effects, meaning that even asymptomatic cats will test positive for its antibodies. Not to mention that its first two stages presented as something else. Many cats who actually have FIP have been incorrectly diagnosed with, and treated for, systemic toxoplasmosis or deep fungal infections. There was simply no way to know. Testing for FIP is still a hit-or-miss process; there is no real blood or tissue test that will identify it as the culprit.

The First Hope: GS Treatment

Thankfully, due to a protease-inhibiting drug known as GS-441524, FIP is no longer an automatic death sentence for cats. It's finally treatable! Treatment is lengthy -- up to twelve weeks, followed by a twelve-week observation period -- and pricey, in the thousands of dollars. Dosages and length of treatment vary depending on the cat's age and how far the disease has progressed.

Both veterinarians and cat parents at home are successfully using GS to treat FIP cats. It's available for injection and also in pill form. The injections are recommended for cats who have begun to experience the second-stage gastrointestinal symptoms. Mutian makes the most common brand of the drug. 

Some study participants supplemented the GS with steroids or vitamins B1 or B12, while others also gave gabapentin along with it. More than a quarter of study participants also supplemented the treatment with subcutaneous fluids. The only side effects appeared to be pain and wounds or lesions at the injection site. The treatment did not prove as effective against the ocular or neurological forms of FIP due to the blood-brain barrier preventing it from getting to the location of the problem, but it was more effective against the wet form.

So, what if GS treatment doesn't work for your cat? Over 96% of the 393 cats in the leading study on GS survived, but only 54% of them were considered to be cured of the disease. Close to 13% of them suffered a relapse during the observation period included in the study. What if your kitty goes into remission for a while, then starts experiencing FIP symptoms again? Can the GS series of treatments be used again? Is that advised?

A New Hope: Molnupiravir

In stepped the Every Cat Health Foundation with a grant to study another approach to treating FIP. The researchers announced their results recently, showing that the drug Molnupiravir is proving effective not only for recurring cases of FIP, but as an initial treatment for the disease. It can be given in lieu of additional GS treatment, as well, for cats who are not responding to the GS series of treatments within a few weeks. 

Length of treatment with Molnupiravir was similar to that for GS. Of the 26 cats studied, one relapsed did not survive. Another died from a prolonged seizure after treatment was completed. 92% showed improvement after only three weeks of treatment, over 84% in two weeks, and over 46% within one week. All but one continued treatment for the full term, until they reached the point of complete remission. One cat actually reached remission sooner.

Like the GS treatment, Molnupiravir is available in both injectable and pill forms. Aura makes two formulations of it, and it's reportedly more financially accessible than GS, although it will still set you back more than a few thousand dollars. It does have some occasionally reported side effects, so make sure to ask your veterinarian if it is safe for your cat and which of the two drugs may be the better approach. And keep in mind that the sample size for this study was relatively small, a tenth of the number of cats included in the GS study. Another field study of Molnupiravir included 286 cats, a comparable number to those in the main GS study, and delivered similar results, percentage-wise.

Hope, however, is now a reality. As Molnupiravir, or combined GS-Molnupiravir treatments for FIP become more widely known and used, we will learn more about its effectiveness. Interestingly enough, Molnupiravir is also being used to treat some humans with COVID-19, and GS-441524 is a component of the drug Remdesivir that's used to treat COVID-19. Turns out, we have more in common with our cats than we thought.

Sources: "New Study -- Molnupiravir as new therapeutic option for relapsed FIP cats" published November 7, 2022 on Every Cat Foundation blog; Sarah Jones, Wendy Novicoff, Julie Nadeau, and Samantha Evans, "Unlicensed GS-441524-Like Antiviral Therapy Can Be Effective for Home Treatment of Feline Infectious Peritonitis" published July 30, 2021; Meagan Roy, Nicole Jacque, Wendy Novicoff, Emily Li, Rosa Negash, and Samantha J. M. Evans, "Unlicensed Molnupiravir is an Effective Rescue Treatment Following Failure of Unlicensed GS-441524-like Therapy for Cats with Suspected Feline Infectious Peritonitis" published October 20, 2022; Niels C. Pederson, DVM, PhD of UC Davis, "Neurological and ocular FIP" published April 29, 2019; Niels C. Pederson, DVM, PhD of UC Davis, "Alternative treatments for cats with FIP and natural or acquired resistance to GS-441524" published November 3, 2021; Khan Sharun, Ruchi Tiwari, and Kuldeep Dhama, "Protease inhibitor GC376 for COVID-19: Lessons learned from feline infectious peritonitis" published December 28, 2020